I have an extra 20 gallon tank laying around and im planing on turning it into a quarintine tank. Is that big enough? And all il need is a filter and a light right? Or are there other things ill need? Thanks in advanced!!
That's fine unless you plan on keeping very large fish. You don't need a light. It would be more stressful on a new or recovering fish actually. The best way to do a QT in my opinion is just run the extra cartridge on a running tank and when you need to quarantine just set up the tank throw the filter cartridge in and your cycled. Once your done you could throw out that cartridge and put a new one on your running tank for the next time.